Associated PressThe four Democratic candidates vying to succeed the late Sen. Edward Kennedy, from left, Massachusetts Attorney General Martha Coakley, representative Michael Capuano, Celtics co-owner Stephen Pagliuca, and City Year co-founder Alan Khazei, prepare for their last televised debate in Newton on Wednesday night.NEWTON — The four Democrats vying to succeed the late Sen. Edward M. Kennedy were united Wednesday in saying they oppose a planned U.S. troop buildup in Afghanistan, but they split on a war tax to fund it.

City Year co-founder Alan Khazei kicked off the primary campaign's final televised debate by saying he would support a special levy to fund the 30,000-troop buildup outlined by President Barack Obama.

Attorney General Martha Coakley also said she would consider it, but Rep. Michael Capuano and Boston Celtics co-owner Stephen Pagliuca said they would not.

All four were making what amounted to their closing argument before Tuesday's party primaries.

"I would vote for a tax for a moral war, if I thought it was right," said Capuano. "I will not vote, not only for taxes, I will not vote for funding for this surge, either, as I have not voted for the funding in Iraq, either."

The six-term congressman also was involved in another debate flashpoint. He and Pagliuca renewed an argument from a debate Tuesday about whether Pagliuca's acceptance of a health care amendment banning federal funding for abortion services would trigger a return to so-called back-alley abortions.

Pagliuca accused Capuano of demagoguery akin to recent warnings about health care "death panels," saying, "You're going to be the Sarah Palin of the Democratic Party."

Capuano chuckled at the remark, retorting, "That's the funniest line of the night."

The debate was sponsored by New England Cable News and featured questions asked by three reporters, as well as of the candidates by each other.

On a matter of current events, the candidates were asked whether public figures such as golfer Tiger Woods, who admitted Wednesday to "transgressions" amid tabloid reports of extramarital affairs, should have an expectation to privacy.

Capuano, Pagliuca and Khazei expressly said they personally had nothing to hide; Coakley was not asked the specific question. But all said an examination of their lives was fair game. Coakley warned, however, that an excessive focus would deter people from running for political office.

"Why are we so obsessed with Tiger Woods and his life?" asked a clearly exasperated Khazei. "People need to know that we care about them and will deliver for them."

Two candidates are also competing next week for the Republican nomination: state Sen. Scott Brown and Duxbury attorney Jack E. Robinson. The party finalists will square off Jan. 19 in the general election.

Kennedy died Aug. 25 of brain cancer. He has been replaced on an interim basis by Paul G. Kirk Jr., former chairman of the Democratic National Committee.